Container



April l, 1947- H. E. GRIFFITH 2,418,172

CONTAINER l Filed Nov. 7, 1941 fsw INVENTO MY A TroRNEY Patented Apr. l, 1947 CONTAINER Henry E.`Griiith, Hartford, Conn., assigner to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware Application November '7,4 1941, Serial No. 418,233

4 Claims.

This invention relates to containers having a novel inner liner in combination with walls having a self-sealing structure capable of sealing a hole made therein as by such a projectile as a bullet, and more particularly pertains to a `selfsealing gasoline tank, especially `suitable for a military airplane, having a novel inner liner in combination with the self-sealing means.

The construction of such a tank as one suitable for a military airplane, for example, which will be not only self-sealing when punctured or traversed as by such a projectile as a bullet but also otherwise satisfactory as a tank for such motor fuel as gasoline has long presented a very difficult problem. When a high velocity bullet passes through a tank containing a liquid such as gasoline, a pressure wave is set up in the liquid as the bulletpasses through it creating a liquid hammer or ram effect against the opposite wall of the tank from which the bullet entered. The result of this is a tendency to tear out a large hole where the bullet leaves the tank. This creates a special problem in constructing a self-sealing tank subject to being traversed or punctured by a bullet, since, in addition to overcoming the tendency described above, such a tank must also be otherwise satisfactory for the purpose intended. The kind of a container to which this invention particularly relates is a self-sealing gasoline tank,

-which may, for example, have walls comprising,

from the outside toward the inside, a layer of very heavy hide leather, a layer of latex approximately 1L., inch thick, a layer of sponge rubber about 1/4 inch thick, another layer of latex about le inch thick, a layer of split hide, and an inner liner which is contacted by the gasoline.` The inner liner serves to retain or hold the gasoline, and the other layers serve as a support and as a self-sealing means when the wall is traversed by a bullet. When a bullet passes through such a wall properly constructed in accordance with this invention, it appears that the sponge rubber tends to push into the hole to prevent substantial leakfge of the gasoline, while the latex swells, when contacted by the gasoline, and expands to eiect a sealing of the hole. The leather and hide impart strength and some rigidity to the tank wall.

The requirements for a satisfactory -inner liner for such a container are numerous and exacting. Such a liner must not only cooperate with the self-sealing means in its function but also must serve as a satisfactory retainer for the contents,

such as gasoline, of the container. lAmong the chief disadvantages of prior art materials used for inner liners of containers of the kind referred at an undesirably high rate, that the material would permit extraction of substances by the contents of the container which would contaminate the contents rendering them unsuitable for the purpose intended, (gasoline, for example, might be contaminated so asto be harmful to the motor when used as motor fuel), that when traversed by a bullet the liner would be shattered, thus exposing the outer layers of the tank walls to the contents of the tank, or that the material of the liner after being traversed by the bullet, especially from the inside toward the outside accompanied by the liquid hammeror ram effect, would be expanded or torn out in such a way as to hold open the hole left by the bullet by expanded protruded portions extending into the hole so that the self-sealing means could not function properly. Although one kind of a material might be more or less satisfactory so far as many of the requirements are concerned, it would nevertheless have sufficient disadvantage to render the container highly unsatisfactory in some particular respect. For example, even though a thin sheet of aluminum might be more or less satisfactory so far as many of the re quirements are concerned, it has the outstanding disadvantage that the liquid ram effect, referred to above, usually leaves a large hole torn in the 'sheet with portions protruding into the hole preventing the functioning of the self -sealing means. Moreover, other materials, for example, numerous synthetic materials, even though satisfactory to some extent with regard to one or some of the requirements, are unsatisfactory as to other important factors.

It is an object of this invention-to provide a self-sealing container which avoids the foregoing disadvantages.

It is a further object of this invention to provide a self-sealing container having a novel inner liner in combination with the `outer wall structure including the self-sealing means which improves the container.

Another object of this invention is to provide having a self-sealing wall structure, especially a container or tank for such hydrocarbons as gasoline, benzene, lubricating oil, etc. The polyvinyl acetal resins described in U. S. Letters Patent to Morrison et al., Reissue No. 20,430, issued June 29, 1937, and in French Patent No. 793,175 exemplify resins suitable for the purpose of this invention. These resinous compositions are tough, elastic and flexible, and an inner liner made in accordance with this invention cooperates with the rest of the wall structure, including the self-sealing means, to produce remarkably improved results in a self-sealing container, especially a gasoline tank for a military airplane, for example.

The liners made in accordance with this invention do not corrode, as metals, for example, are resistant to deterioration by water or such contents as hydrocarbons including gasoline, benzene, lubricating oils, etc., have a surprisingly low average rate of diffusion therethrough by suchmaterials as gasoline, do not permit extraction of substances by hydrocarbons which would contaminate the contents of the container, especially such hydrocarbons/as gasoline, benzene, lubricating oil, for example, are tough. elastic and flexible and cooperate with the outer wall layers, which include the self-sealing means, to make it possible to make a wall such that, even a high speed bullet passing through the liquid contents and -out through the wall accompanied by the liquid hammer or ram effect, produces only such '4 that such outer layers include an element efective to seal a hole made by a. projectile and that the outer layers be such that the wall structure as a whole is suiiiciently strong, elastic and nontearing that a projectile passing therethrough leaves a hole `having a sufciently small opening that the sealing means can function properly.

The inner liner 1 comprising the polyvinyl acetal -is preferably in the form of a relatively thin a hole as can readily be sealed by the self-sealing means. l 4 Inorder to illustrate and exemplify this invention, one embodiment thereof will be described in connection with the accompanying drawing, but it is to be understood that my invention is not necessarily limited thereto and that this embodiment is presented principally by way of illustration and exemplii'ication of this invention and not limitation. In the drawing, Fig. l shows a tank constructed in accordance with this invention; y and Fig, 2 shows the inner layers of the Wall structure in detail.

' A tank is shown generally at I, which ,may have an outer envelop 2, usuallyof metal such as aluminum. Referring more particularly to Fig. 2, which shows an enlargement in detail of the inner wall structure in accordance with this invention without an outer envelop as shown in Fig. 1 at .2, the outer layer of the inner wall structure is shown lat 3, which may comprise a tough wear-resistant material such as a rubber impregnated rayon, for example. Layers 4 and 6 comprise a material which swells and expands when contacted by the contents of the container to effect a sealing of a hole left as by a projectile, and for such hydrocarbons as gasoline, benzene and lubricating oils, for example, especially gasoline, a material such aslatex is satisfactory.

At 5 is a layer of such a material as vulcanized rubber which adds elasticity to the wall strucl ture as a whole, and appears to cushion the shock of a high speed projectile. The inner lining is shown at I and comprisesa polyvinyl acetal resin in accordance with thisinvention.

It is to be understood that other outer layers of wall structure may be used in combination with the novel inner liner of this invention, but that for a self-sealing container it is highly desirable sheet of suoli a resin. It may, however, with some advantage comprise acoating of such a resin applied to the inner surface of the outer layers, and, moreover, may be made by coatin various degrees and under different conditions-.

before hydrolysis and reaction with the aldehyde. Moreover, the resulting acetals may contain different proportions of ester, hydroxyland acetal groups corresponding to the degree of hydrolysis and acetalization of the polymerized ester. It is,

desirable to select those polyvinyl acetal resins which are least affected or substantially unaffected by the contents of the container; for example, for a. gasoline tank, it is desirable to use v those polyvinyl acetal resins which are gasoline insoluble or the least affected by gasoline. For example, a polyvinyl acetal suitable for this invention results from the polymerization of. vinyl acetate to such a degree that a one-molar solution of the polymer in benzene `had a viscosity of substantially 25 centipoises at 20 C., and the hydrolysis and reaction of the polyvinyl acetate with butyraldehyde to form a polyvinyl acetal resin containing substantially 17 to 21 per cent hydroxyl groups calculated as polyvinyl alcohol, 3% or less acetate group calculated as polyvinyl acetate, by weight, and the rest acetal.

Polyvinyl formaldehyde acetals such as disclosed inthe patents referred to above may also be used. Thus, the polyvinyl formal'resulting from the polymerization of vinyl acetate to such a degree that a one-molar solution of the polymer in benzene had a viscosity of substantially 18 to 22 centipoises at 20 C. and hydrolyzed and reacted with formaldehyde to form a polyvinyl formaldehyde acetal resin containing substantially 5 to 6% hydroxyl groups calculated as polyvinyl alcohol, y9.5 to 13% acetate calculated as polyvinyl acetate, by weight, and the rest acetal, is an'example of a, polyvinyl acetal suitable for the present invention. Moreover, this invention comprehends the use of other aldehydes, such as acetal'dehyde, or mixtures thereof or even ketones in making suitable polyvinyl acetals to be used in accordance with this invention. Thus, for example, acetaldehyde, propionaldehyde, valeraldehyde, and hexaldehyde may be used. In general it is desirable to use a resin which will not be 'deteriorated to any substantial extent by the hyde or butyraldehyde is preferred.

The illm or sheet'of polyvinyl acetal for this invention may be made by any of the known methods of forming such a resin into a iilm or sheet, which should, of course, be nonporous for a fluid container. The resin may be extruded by means of suitable apparatus to produce a sheet, or a solution of the resin in a suitable solvent may be cast in any well-known manner and a iilrn or sheet formed by evaporation of the solvent. Sheets of any desired thickness may be formed by these methods and a thickness of about .025 inch is usually suitable.

In general any of the known plasticizers for polyvinyl acetal resins` may be used in the resin i1' desired. For example, diethyl phthalate, di,- acetin, dimethyl phthalate, 'dimethoxy ethyl phthalate, ethyl ethoxy ethyl phthalate, triacetin, methyl-or ethyl phthalyl ethyl glycollate, triethylene glycol dibutyrate, diethylene glycol dipropionate, triethylene glycol dihexoate, dibutyl or dimethyl sebacate, triethylene glycol esters of cocoanut oil acids, and others, may be used for the polyvinyl formal or butyral described above.

What I claim is:

1. In a gasoline container characterized by the ability to self-seal when in contact with gasoline after the passage of a bullet therethrough, a wall having the following consecutive layers: a layer of tough, wear-resistant material, a layer of gasoline-swellable material, a layer of elastic material, another layer of a gasoline-swellable material and an inner layer comprising a gasolineinsoluble polyvinyl acetal resin containing,.by

y weight, from about 5 to `21% hydroxyl groups calculated as polyvinyl alcohol, up to about 13% acetate groups calculated as polyvinyl acetate and the rest substantially acetal.

2. In a gasoline container characterized by the ability to self-seal when in contact with gasoline after the passage of a bullet therethrough, a wall having the following consecutive layers: a layer of rubber-impregnated rayon, a layer of latex, a

layer of vulcanized rubber, another layer of latex and an inner layer comprising a polyvinyl acetal resincontaining, by weight, from 5to 21% hydroxyl groups calculated as polyvinyl alcohol, up to about 13% acetate groups calculated as polyvinyl acetate and the rest substantially acetal.v

30 ille of this patent:

6 3.' In a gasoline container characterized by the ability to self-seal when in contact with gasoline after the passage of a bullet therethrough, a wall having the following consecutive layers: a layer 5 0f a tough, wear-resistant material, a layer of a gasoline-swellable material, a layer of elastic material, another layer of a gasoline-swellable material and an inner layer comprising a plasticized sheet of polyvinyl butyral resin containing,

10 by weight, from about 17 to 21% hydroxyl groups calculated as polyvinyl alcohol, 3% or less acetate groups calculated as polyvinyl acetate and the rest substantially acetal.

4. In a gasoline container characterized by the ability to'self-seal when in contact with gasoline after the passage of a bullet therethrough, a wall having the following consecutive layers: a layer and an inner layer comprising a plasticized sheet of polyvinyl butyral resin containing by weight, from about 17 to 21% hydroxyl groups calculated as polyvinyl alcohol, 3% or less acetate groups calculated as polyvinyl acetate and the rest smb- HENRY E. GRIFFITH.

REFERENCES CITED The following references are of record in the UNITED STATES PATENTS Number Name Date 1,386,791 Murdock Aug. 9, 1920 1,616,116 De Salamanca Feb. 1, 1927 2,039,401 Foges May 5, 1936 2,053,112 Schnabel Sept. l, 1936 2,160,371 Schnabel May 30, 1939 2,267,830 Lewis Dec. 30, 1941 40 1,297,305 Thacker Mar. l1, 1919 1,325,448 Macbeth Dec. 16, 1919 1,779,397 Kraft Oct. 21, 1930 FOREIGN PATENTS 5 Number Country Date v 466,598 British 1937 

